Variable pumping system for a propeller fan

ABSTRACT

An inflatable rubber tube is attached to the interior of a fan shroud for the cooling fan of a reciprocating engine where the tube surrounds the rotation envelope of a fan. A temperature sensing mechanism deflates the tube to increase the clearance space of the fan and thereby decrease pumping efficiency when engine temperature is below its normal operating level. The temperature sensing mechanism inflates the tube to increase pumping efficiency if engine temperature rises above its normal operating level.

United States Patent 1191 11] 3,829,236 Maciiennan Aug. 13, 1974 VARIABLE PUMPING SYSTEM FOR A 2,994,472 8/1961 Botje 415/174 pROPELLER FAN 3,168,870 2/1965 Hornschuch 415/111 [75] Inventor: Alastair S. MacLennan, Farmington, FOREIGN PATENTS R A PLKTATIONS Mic 292,067 10/1928 Great Britain 277/343 721,092 12/1954 Great Britain 415/147 [731 Motor Company Dearbom 957,884 5/1964 Great Britain 415/147 Filedl J 1973 Primary Examiner Henry F. Raduazo Attorney, Agent, or Firm-Keith L. Zerschling; [21] Appl. No.. 368,391 v R. E. Mccollum Related US. Application Data 57 ABSTRACT [62] 5 23 2? May 1972 An inflatable rubber tube is attached to the interior of a fan shroud for the cooling fan of a reciprocating en- [52] U S C] 415/156 415/147 277/34 3 gine where the tube surrounds the rotation envelope [51] F04; 25/12 [364d 27/60 of a fan. A temperature sensing mechanism deflates [58] i 415/146 5 5 174 the tube to increase the clearance space of the fan and H75 277/34 thereby decrease pumping efficiency when engine temperature is below its normal operating level. The [56] References Cited temperature sensing mechanism inflates the tube to increase pumping efficiency if engine temperature UNITED STATES PATENTS rises above its normal operating level. 2,054,142 9/1936 Sharp 415/175 2,447,957 8/1948 Moore 415/174 5 Chums, 4 Drawmg Flgul'es MENIED Mm 319M FIG.2

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VARIABLE PUMPING SYSTEM FOR A PROPELLER FAN This is a Division of application Ser. No. 249,989, filed May 3, 1972 now Pat. No. 3,760,779.

SUMMARY OF THE INVENTION Cooling requirements for vehicle engines vary widely not only because of changing atmospheric conditions but also because of the changing heat rejection rates during various engine operating modes. Numerous mechanisms have been proposed for varying the cooling effectiveness of a vehicle cooling system according to engine requirements. One relatively simple arrangement involves thermally adjustable louvers positioned in front of the vehicle radiator to control air flow through the radiator. Others include thermally responsive clutches for driving the cooling fan at varying rates and thermally responsive mechanisms for varying the pitch of the fan blades. A few of these mechanisms have achieved some degree of commercial success.

This invention provides a relatively inexpensive mechanism for changing the pumping efficiency of a propeller type fan. The invention is useful particularly in an automotive cooling system where it varies the overall effectiveness of the cooling system. In a cooling system for a reciprocating engine including a radiator, a rotatable fan assembly mounted adjacent the radiator for forcing air through the radiator and a shroud mounted radially outward of the fan assembly, the automatic control mechanism of this invention comprises an inflatable member attached to the shroud where the inflatable member surrounds the fan assembly to define the amount of radial clearance between thefan assembly and the shroud. A temperature responsive device that is responsive to the temperature of. the engine is capable of deflating the inflatable member to increase the radial clearance space of the fan when engine temperature is below a predetermined value and of inflating the inflatable member to the desired degree when engine temperature reaches its normal operating level. Changing the size of the clearance space changes significantly the pumping efficiency of the fan and thus varies the overall performance of the cooling system.

The inflatable member can be a hollow elastomeric tube having a circular cross section although tubes of numerous other cross sectional shapes and materials also can be used. A neoprene rubber or some other elastomeric material capable of surviving for useful periods in the environment of a vehicle engine compartment typically is used to make the tube. Reinforcement can be included in the tube material to increase flex life. The outer sector of the tube is attached to the inner surface of the fan shroud which in turn is attached to the vehicle radiator or engine, and the inner sector of the tube preferably has a relatively thin wall so generating subatmospheric pressure within the tube collapses the inner sector of the tube against the inner surface of the fan shroud.

Intake manifold pressure of the engine can be used to produce the subatmospheric pressure for the tube interior. A temperature responsive valve mechanism controls the application of the intake manifold pressure to the tube interior according to the temperature of the engine coolant, the engine cylinder head or some other temperature source.

lnflating or deflating the tube can vary the radial clearance between the tips of the fan and the shroud from minimum values commensurate with conventional vehicle assembly tolerances to values several times larger than the minimum. Such variations in tip clearance for a conventional automotive type cooling fan installation can alter the air flow characteristics of the cooling system by values up to and exceeding 50 percent.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a side elevation of an installation of this invention in an engine cooling system. The Figure shows the relationship of the vehicle radiator shroud and fan assembly to the engine and shows the shroud in section to reveal the relative position of the inflatable tube.

FIG. 2 is an enlarged sectional. view of a portion of the shroud and tube that shows the tube in an inflated condition to minimize the radial clearance at the tips of the fan blades.

FIG. 3 is similar to FIG. 2 except that a subatmospheric pressure within the tube has collapsed the tube to increase the radial clearance from the tips of the fan blades.

FIG. 4 is a sectional view of the valve mechanism.

DETAILED DESCRIPTION Referring to FIG. 1, a reciprocating internal combustion engine 10 is mounted in a vehicle engine compartment behind a radiator 12. A propeller type cooling fan 14 is positioned between radiator 12 and engine 10 and is mounted rotatably on a shaft 16 that is driven by the engine. A shroud 18 is attached to the radiator or radiator support members (not shown) and extends rearwardly from radiator 12 to surround fan 14.

The inner surface of the rearward portion of shroud 18 has a semi-circular groove that faces the tip portion of fan 14, and a circular inflatable tube 20 is positioned in the groove. Tube 20 is made of an elastomeric material such as neoprene rubber and. it is located radially outward of the tip envelope of fan 14. A conduit 22 connects the interior of tube 20 through a temperature responsive valve mechanism 24 to the intake manifold (not shown) of engine 10. Thevalve mechanism 24 can be of a known construction, for example, such as is shown in FIG. 3 on page 23-15-02 of the Ford 1972 Car Shop Manual, Vol. 2, Engine, published by Ford Marketing Corporation, First Printing, October 1971, and illustrated herein as FIG. 4.

More specifically, FIG. 4 shows a valve body 26 having a hollow interior connected by three ports 28, 30 and 32 respectively connected to atmospheric pres sure, to the tube connecting conduit 22, and to engine intake manifold vacuum. A ball valve 34 is spring biased against a knife-edge seat 36 to connect the intake manifold vacuum in port 32 to conduit 22 while simultaneously blocking the atmospheric pressure in port 28.

A plunger 38 is spring biased away from the ball valve 34, and is engaged at its lower end 40 by a member 42 moved upwardly at times by an encased wax pellet 44. The pellet is submerged into the engine liquid cooling system so as to be subject to the changes in engine operating temperatures.

When valve mechanism 24 senses an engine temperature within or below the normal operating range, the wax pellet is in a solid state and exerts no pressure on the plunger 38. Therefore, the valve mechanism applies the subatmospheric pressure existing port 32 from in the engine intake manifold to the interior of tube 20. The subatmospheric pressure within tube collapses the tube to the shape shown in FIG. 3 thereby increasing the radial clearance at the tip portions of fan 14. Fan pumping efficiency and noise are reduced and the ram effect of air through the radiator is maximized.

When engine temperature exceeds the normal operating range, the wax pellet begins assuming a liquid state and the pressure of expansion unseats ball valve 34. Thus, the valve mechanism 24 disconnects the interior of tube 20 from the engine intake manifold and applies instead the higher atmospheric pressure. Tube 20 expands to the configuration shown in FIG. 2, which decreases the radial clearance of fan 14 and thereby increases the overall performance of the cooling system.

The system of the invention can be used in a variety of different ways to control engine temperature. For example, subatmospheric pressure can be applied to the interior of tube 20 whenever vehicle speed exceeds a predetermined value. At speeds above the predetermined value, the large tip clearance reduces fan noise and maximizes the effect of ram air to produce highly efficient radiator performance. At speeds below the predetermined value, a higher absolute pressure is applied to the interior of tube 20 to inflate the tube to the configuration shown in FIG. 2. The resulting increase in fan performance assists in maintaining engine operating temperature within its normal range.

A relatively simple on-off valve mechanism 24 can be used to produce either the fully collapsed or fully inflated configuration of tube 20 as shown in the drawings. If greater control is desired, a valve mechanism 24 that modulates the internal pressure of tube 20 can be substituted to produce a variety of intermediate configurations of tube 20. Interior pressure for tube 20 can be provided by any of several sources such as the power steering system, the engine lubricating system, the automatic transmission fluid or an independent system that is designed specifically to supply the tube interior.

In a typical automotive installation, tube 20 is formed of a reinforced flexible material that biases the tube into a fully formed configuration as shown in FIG. 2 when its internal pressure substantially equals its external pressure. The clearance between the tips of the fan blades and the tube is about "/1. inch (smaller clearances can be used if the fan shroud 18 is mounted on the engine). When engine temperature is below a predetermined value, engine intake manifold vacuum collapses the tube to the FIG. 3 configuration, thereby increasing radial tip clearance to about 1% inches. The resulting decrease in fan noise and increased use of ram air greatly improves overall cooling system performance.

Thus this invention provides an automatic control mechanism for varying the performance of a propeller type fan. The invention is useful particularly in vehicle cooling systems but can be applied to other installations of propeller type fans.

I claim:

1. In a pumping system including a fluid impeller element mounted rotatably within a shroud, a control mechanism for varying the pumping efficiency of the impeller element comprising inflatable means attached to the shroud and surrounding the rotatable impeller element and being positioned between the shroud and the impeller element to define a radial clearance space, and control means for varying the pressure within said inflatable means to contract or expand the inflatable means and thereby vary the radial clearance space,

the control means comprising pressure control means responsive to temperature changes to reduce the pressure within the inflatable means and thereby increase the clearance space when temperature is below a predetermined value.

2. The pumping system of claim 1, in which the inflatable means is a hollow elastomeric tube.

3. The pumping system of claim 1, in which the elastomeric tube is in a fully formed configuration when the pressure within the tube substantially equals the pressure outside of the tube.

4. The pumping system as in claim 2, wherein the pressure control means comprises a variable source of vacuum.

5. The pumping system as in claim 4, wherein the inflatable means is collapsed when the pressure within is reduced to a value below the pressure outside the inflatable means. 

1. In a pumping system including a fluid impeller element mounted rotatably within a shroud, a control mechanism for varying the pumping efficiency of the impeller element comprising inflatable means attached to the shroud and surrounding the rotatable impeller element and being positioned between the shroud and the impeller element to define a radial clearance space, and control means for varying the pressure within said inflatable means to contract or expand the inflatable means and thereby vary the radial clearance space, the control means comprising pressure control means responsive to temperature changes to reduce the pressure within the inflatable means and thereby increase the clearance space when temperature is below a predetermined value.
 2. The pumping system of claim 1, in which the inflatable means is a hollow elastomeric tube.
 3. The pumping system of claim 1, in which the elastomeric tube is in a fully formed configuration when the pressure within the tube substantially equals the pressure outside of the tube.
 4. The pumping system as In claim 2, wherein the pressure control means comprises a variable source of vacuum.
 5. The pumping system as in claim 4, wherein the inflatable means is collapsed when the pressure within is reduced to a value below the pressure outside the inflatable means. 